1. Field of the Invention
The present invention relates generally to an optical triangulation displacement sensor using a diffraction grating, and more particularly to an optical triangulation displacement sensor using a diffraction grating, in which a transmission grating is disposed between an image formation lens and a light-receiving element so that a light ray having passed through the image formation lens is divided into a plurality of light rays by the diffraction grating and the diffracted light rays form an image in the light-receiving element. That is, the present invention relates to an optical triangulation displacement sensor using a diffraction grating, which is capable of averaging errors caused by the noise of a light-receiving element by applying an arithmetic mean method in the same size of that for a conventional sensor head within the same sampling time.
2. Description of the Prior Art
FIG. 1 is a schematic diagram of a conventional optical triangulation displacement sensor. FIG. 2 is a graph showing the optical intensity distribution of the light-receiving element shown in FIG. 1. As depicted in FIGS. 1 and 2, a light source element 100 generating light of certain intensity emits light to a condenser 200, and the condenser 200 passes light to a surface of measurement 10. The light incident upon the surface of measurement 10 is reflected, passes through an image formation lens 300, and forms certain strength distribution in a light-receiving element. As the surface of measurement moves, the light intensity distribution also shifts.
In this case, when the peak position of the light intensity distribution is extracted by a signal processor unit 600, the positional information of the surface of measurement 10 with regard to the peak position of the light intensity distribution can be obtained and that is linear relation.
In the conventional optical triangulation displacement sensor 700, measurement is performed several times and measured values are averaged to reduce effects of errors. In the conventional optical triangulation displacement sensor 700, various noises affecting optical intensity distribution assume random noise patterns. If the measurement values are averaged, there occur problems that excessive time is required for measurements because of a decrease in the standard deviation of the noises and errors are caused by the movement of the surface of measurement.
In order to solve the problems, a plurality of light-receiving elements 500 are suitably arranged in the conventional optical triangulation displacement sensor 700, and values measured by the elements 500 are utilized in a mean form. The conventional optical triangulation displacement sensor 700 employs a plurality of light-receiving elements and averages measured values, so there occur problems that the size of sensor head should be enlarged and excessive costs are incurred.
The errors of the optical triangulation displacement sensor 700 caused by a variation in the output of a light source can be reduced by sensing the output of the light source in a real time. However, other errors can be caused by other factors, so there occurs a shortcoming that the size of a sensor head should be enlarged.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide an optical triangulation displacement sensor using a diffraction grating, in which a transmission grating is disposed between an image formation lens and a light receiving-element so that a light ray having passed through the image formation lens is divided into a plurality of light rays by the diffraction grating and the diffracted light rays form an image in the light-receiving element. Finally, several results of the surface of measurement are detected simultaneously, the new measurement result can be obtained by averaging them. That is, the present invention relates to an optical triangulation displacement sensor using a diffraction grating, which is capable of averaging errors caused by the noise of a light-receiving element by applying an arithmetic mean method in the same size of that for a conventional sensor head within the same sampling time.
In order to accomplish the above object, the present invention provides an optical triangulation displacement sensor using a diffraction grating, comprising a light source element for generating light of certain intensity, a condenser for receiving the light from the light source element and transmitting the light to the surface of measurement, an image formation lens for receiving the light reflected by the surface of measurement, a transmission grating for converting the reflected light having passed through the image formation lens into a plurality of diffracted light rays, and a light-receiving element in which an image is formed by the diffracted light rays incident from the transmission grating.
The optical triangulation displacement sensor may further compromise a transmission grating, the transmission grating being situated between the image formation lens and the light-receiving element.
In the optical triangulation displacement sensor, an image formed in the light-receiving element is transmitted to a signal processing unit, and the positional information of the surface of measurement with regard to the optical triangulation displacement sensor is acquired by the signal processing unit.
In the optical triangulation displacement sensor, diffracted light rays having passed through the transmission grating create optical intensive distribution of a certain pattern in the light-receiving element.
In the optical triangulation displacement sensor, diffracted light rays generated by the transmission grating form an image in the light-receiving element to be arithmetically averaged within a predetermined sampling time.
In the optical triangulation displacement sensor, the light-receiving element may be a CCD light-receiving element that is capable of acquiring entire optical intensity over space.
In the optical triangulation displacement sensor, diffracted light rays generated by the transmission grating may be xe2x88x921-order light ray, 0-order light ray and +1-order light ray.